A night vision goggle (NVG), which is well known in the art, is an optical device that allows images to be produced in levels of light approaching total darkness. NVG's are most often worn by the military and law enforcement personnel, whose health and safety are of the utmost importance.
The present invention is directed to apparatus, systems, and methods for monitoring movement of one or more eyes, eyelids, and/or pupils of an NVG user. Monitoring the eye movement of the NVG user is useful in determining whether that NVG user is either unconscious or incapacitated, and therefore requires assistance.
As described in U.S. Patent App. Pub. No. 2011/0077548 to Torch, which is incorporated by reference herein in its entirety, humans blink at least about 5-30 times per minute. Each involuntary-reflexive blink lasts about 200-300 milliseconds, generally averaging about 250 milliseconds. As tiredness or sleepiness occurs, the eye blink may get longer and slower and/or the blink rate may vary, and/or the eyelids may begin to droop with small amplitude eye lid blinks, e.g., until the eyes begin to close for short term “microsleeps,” i.e., sleep conditions that last for about 3-5 seconds or longer, or for prolonged sleep.
Furthermore, the pupils may constrict more sluggishly, show unstable fluctuations in size, shrinking progressively in diameter, and/or demonstrate delayed responses to light flashes (i.e. delayed pupil response latency) as sleepiness and fatigue progresses. In addition, other ocular manifestations of drowsiness may occur, such as slow or delayed saccadic eye tracking responses, e.g., to a stimulus (i.e., delayed saccadic response latency), with either over- or under-shooting the target, and/or a loss of directed gaze with or without binocular vergence or divergence, eye drift, or esophoria.
Thus, monitoring the movement of one or more eyes, eyelids, and/or pupils of an NVG user would help determine whether that user requires immediate assistance.